Note: I'm not repeating Pokemon, so once one's mentioned, it won't appear in the list again.

Bug: Venonat, Beedrill, and Volbeat
Why: Venonat because it's cute. Beedrill for nostalgic reasons (and because the one I have in Fire Red is awesome for in-game battling). Volbeat because it's awesome in-game too.

Electric: Raichu and Electabuzz
Why: Both nostalgic reasons and because I've always found it cute. It was my original favorite Pokemon and thus served on all of my teams back in my RBY days. Electabuzz, meanwhile, is there for in-game reasons. I've got one on my Fire Red team that's known to kick tail and wipe the floor with the Elite Four.

Flying: Farfetch'd and Crobat
Why: I've always loved how quirky Farfetch'd is, and a Farfetch'd used to be my best Pokemon on my RBY teams (back before I learned the power of EVERY OTHER FLYING POKEMON). Crobat, meanwhile, serves on my Sapphire team as one of my four strongest Pokemon. It seriously kicks tail before my opponents even realize it.

Ghost: Haunter
Why: I blame this completely on the anime.

Grass: Cradily
Why: Because it's quirky and one of the best contest Pokemon I have in Sapphire.